Photolithography mask with protective silicide capping layer

Abstract

A photomask and a method of fabricating the photomask. The photomask including: a substrate transparent to a selected wavelength or wavelengths of radiation, the substrate having a top surface and an opposite bottom surface, the substrate having a printable region and a non-printable region; the printable region having first opaque regions raised above the top surface of the substrate adjacent to clear regions, each opaque region of the first opaque regions having sidewalls and opposite top and bottom surfaces, the first opaque regions including a metal; the non-printable region including metal second opaque region raised above the top surface of the substrate, the second opaque region having sidewalls and opposite top and bottom surface, the second opaque regions including the metal; and a conformal protective metal oxide capping layer on top surfaces and sidewalls of the first and second opaque regions. The conformal layer is formed by oxidation.

1 . A photomask, comprising:
 a substrate transparent to a selected wavelength or wavelengths of radiation, said substrate having a top surface and an opposite bottom surface, said substrate having a printable region and a non-printable region;   said printable region having first opaque regions raised above said top surface of said substrate adjacent to clear regions, each opaque region of said first opaque regions having sidewalls and opposite top and bottom surfaces, said first opaque regions comprising a metal;   said non-printable region comprising metal second opaque region raised above said top surface of said substrate, said second opaque region having sidewalls and opposite top and bottom surface, said second opaque regions comprising said metal; and   a conformal protective metal silicide capping layer on top surfaces and sidewalls of said first and second opaque regions.   
     
     
         2 . The photomask of  claim 1 , further including:
 said printable region divided into first printable regions and second printable regions; and   trenches extending from said top surface of said substrate into said substrate in said first printable regions where said substrate is not covered by said first opaque regions, said bottom surfaces of said first opaque regions covered by said capping layer where said bottom surfaces of said first opaque regions overhang said trenches.   
     
     
         3 . The photomask of  claim 1 , further including:
 said printable region divided into first printable regions and second printable regions;   a first set of trenches extending from said top surface of said substrate into said substrate in said first printable regions where said substrate is not covered by said first opaque regions, said bottom surfaces of said first opaque regions covered by said capping layer where said bottom surfaces of said first opaque regions overhang said trenches;   a second set of trenches extending from said top surface of said substrate into said substrate in said second printable regions where said substrate is not covered by said first opaque regions, said bottom surfaces of said first opaque regions covered by said capping layer where said bottom surfaces of said first opaque regions overhang said trenches; and   wherein said trenches of said first set of trenches extend into said substrate a first distance from said top surface of said substrate, said trenches of said second set of trenches extend into said substrate a second distance from said top surface of said substrate, said first distance different from said second distance.   
     
     
         4 . The photomask of  claim 1 , wherein said protective capping layer comprises a silicide of said metal. 
     
     
         5 . The photomask of  claim 1 , wherein said metal comprises chrome and said protective capping layer comprises chrome silicide. 
     
     
         6 . The photomask of  claim 1 , wherein said capping layer has a thickness between about 10 Å and about 50 Å. 
     
     
         7 . A method, comprising:
 on a substrate transparent to a selected wavelength or wavelengths of radiation, said substrate having a top surface and an opposite bottom surface, defining a printable region and a non-printable region;   forming in said printable region, first opaque regions raised above said top surface of said substrate adjacent to clear regions, each opaque region of said first opaque regions having sidewalls and opposite top and bottom surfaces, said first opaque regions comprising a metal;   forming in said non-printable region, metal second opaque region raised above said top surface of said substrate, said second opaque region having sidewalls and opposite top and bottom surface, said second opaque regions comprising said metal; and   forming a protective metal silicide capping layer on top surfaces and sidewalls of said first and second opaque regions.   
     
     
         8 . The method of  claim 7 , further including:
 dividing said printable region into first printable regions and second printable regions;   after said forming said protective metal silicide capping layer, etching trenches into said substrate in said first printable regions where said substrate is not covered by said first opaque regions; and   where said forming said capping layer does not form said capping layer on said bottom surfaces of said first opaque regions that overhang said trenches.   
     
     
         9 . The method of  claim 7 , further including:
 dividing said printable region into first printable regions and second printable regions;   after said forming said protective metal silicide capping layer, etching a first set of trenches into said substrate in said first printable regions where said substrate is not covered by said first opaque regions followed by etching a second set of trenches into said substrate in said second printable regions where said substrate is not covered by said first opaque regions;   said capping layer is not formed on said bottom surfaces of said first opaque regions that overhang said first set of trenches and said capping layer is not formed on said bottom surfaces of said second opaque regions that overhang said second set of trenches; and   wherein said trenches of said first set of trenches extend into said substrate a first distance from said top surface of said substrate, said trenches of said second set of trenches extend into said substrate a second distance from said top surface of said substrate, said first distance different from said second distance.   
     
     
         10 . The method of  claim 7 , wherein said forming said capping layer comprises:
 depositing a silicon layer onto all exposed surfaces of said first and second opaque regions and said top surface of said substrate in said clear regions;   annealing said silicon layer at a temperature of about 500° C. or higher in an inert atmosphere to form said metal silicide; and   removing any unreacted silicon layer.   
     
     
         11 . The method of  claim 7 , wherein said metal comprises chrome and said capping layer comprises chrome silicide. 
     
     
         12 . The method of  claim 7 , wherein said capping layer has a thickness between about 10 Å and about 50 Å.